A sells an article to B at a profit of 10% B sells the article back to A at a loss of 10%. In this transaction:

Let CP was 100 for A originally A sells article to B at 10% profit, CP for B = 100 + 10% of 100 = 110 Now, B sells it A again with loss 10% Now, CP for A this time = 110 - 10% of 110 = 99 A makes Profit = 110 - 99 = 11 %profit for A = (11×100)/100 = 11% Second Method It could be easily shown by net percentage change graphic. 100(A) == 10%(Profit) ⇒110(B) == 10%(Loss) ⇒ 99(A) In this transaction A makes a profit of (110 - 99 = 11%) 11% [10% on selling to B and 1% profit on buying back from B]